Who Ate What

For Chang's study to work, each veteran had to get all his food from the assigned kitchen. That way, the veteran only got potassium-enriched salt or regular salt. Grazing from kitchen to kitchen would muddy the data.

The test kitchens switched their salt gradually over a month. The veterans knew about the experiment, but they didn't know what type of salt was in their food.

A total of 768 veterans ate from the kitchens using potassium-enriched salt. Another 1,213 veterans got their food from kitchens using regular salt.

When the study started, most veterans were at least 65 years old. Their age, weight, and blood pressure were similar, with about 40% having high blood pressure. None was bedridden or had kidney problems. People with kidney problems should not take extra potassium in order to avoid problems such as abnormal heart rhythms.

Fewer Heart Deaths

The veterans were followed for 2.6 years, on average. During that time, 504 veterans died.